1. Field of the Invention
The invention relates to a method and apparatus for monitoring size encapsulation of yarn on a slasher.
2. Description of the Prior Art
Size encapsulation is a measure of the degree that a starch or other film covers the surface of the yarn making up a warp preparatory to weaving.
The sizing machine or slasher generally utilizes a hot liquid starch bath into which several thousand individual strands or ends of yarn which make up the warp are immersed. After immersion, excess liquid is squeezed out by passing the warp between tightly compressed squeeze rolls. The warp is then passed over several sets of steam heated drying cylinders which evaporate most of the water. An even dispersion of solid starch is left on the yarn in the form of a coating. The starch penetrates the soft yarn, and this helps to keep it from breaking off. Size encapsulation is expressed in degrees from 0 to 360 as an average measure of coverage around the yarn.
Very fine hairs protrude from the surface of spun yarn before it is sized and one of the main objects of sizing is to bind these hairs to the yarn and to cover both with the smooth size film to protect the bundle of hairs from the abrasive forces of the loom where the warp will be woven into cloth.
After the warp is dried, adjacent ends or strands may be stuck together by excess size. The adjacent ends are separated by pulling them alternately over and under round bars which extend through the entire warp. During this process, some of the size actually covering the hairs breaks off and the hairs once again protrude from the surface of the yarn.
The degree of size encapsulation around each yarn in the warp has always played an important role in reducing loom stops due to warp end breaks. This importance has increased in recent years as a consequence of increasing loom speeds made possible by the use of air instead of a projectile or shuttle to propel the filling yarn through the shed or opening between alternate ends or strands of yarn in the warp.
When numerous hairs protrude from the yarn making up the warp, they impede the air blast and, if sufficiently severe, cause the filling stop motion on the loom to be activated.
This effect was discovered in the mills three years ago, which prompted us to furnish moisture sensors between drying sections on the slasher to assure the optimum amount of moisture in the yarn at the moment it contacts a hot drying cylinder of the final dryer. Our moisture controls are being used now to regulate the steam pressure on the first dryers to achieve this objective.